Support "shared" histograms between processes.

base/metrics/histogram_samples.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/histogram_samples.h"
 
 #include "base/compiler_specific.h"
 #include "base/pickle.h"
 
 namespace base {
@@ skipping 69 matching lines @@
 // atomic! Race conditions may cause loss of samples or even completely corrupt
 // the 64-bit sum on 32-bit machines. This is done intentionally to reduce the
 // cost of these operations that could be executed in performance-significant
 //  points of the code.
 //
 // TODO(bcwhite): Gather quantitative information as to the cost of using
 // proper atomic increments and improve either globally or for those histograms
 // that really need it.
 
 void HistogramSamples::Add(const HistogramSamples& other) {
-#ifdef ARCH_CPU_64_BITS
-  subtle::NoBarrier_Store(
-      &meta_->sum,
-      subtle::NoBarrier_Load(&meta_->sum) + other.sum());
-#else  // No Atomic64 on 32-bit platforms.
   meta_->sum += other.sum();
-#endif
 
   HistogramBase::Count old_redundant_count =
       subtle::NoBarrier_Load(&meta_->redundant_count);
   subtle::NoBarrier_Store(&meta_->redundant_count,
       old_redundant_count + other.redundant_count());
   bool success = AddSubtractImpl(other.Iterator().get(), ADD);
   DCHECK(success);
 }
 
 bool HistogramSamples::AddFromPickle(PickleIterator* iter) {
   int64 sum;
   HistogramBase::Count redundant_count;
 
   if (!iter->ReadInt64(&sum) || !iter->ReadInt(&redundant_count))
     return false;
 
-#ifdef ARCH_CPU_64_BITS
-  subtle::NoBarrier_Store(
-      &meta_->sum,
-      subtle::NoBarrier_Load(&meta_->sum) + sum);
-#else  // No Atomic64 on 32-bit platforms.
   meta_->sum += sum;
-#endif
 
   HistogramBase::Count old_redundant_count =
       subtle::NoBarrier_Load(&meta_->redundant_count);
   subtle::NoBarrier_Store(&meta_->redundant_count,
                           old_redundant_count + redundant_count);
 
   SampleCountPickleIterator pickle_iter(iter);
   return AddSubtractImpl(&pickle_iter, ADD);
 }
 
 void HistogramSamples::Subtract(const HistogramSamples& other) {
-#ifdef ARCH_CPU_64_BITS
-  subtle::NoBarrier_Store(
-      &meta_->sum,
-      subtle::NoBarrier_Load(&meta_->sum) - other.sum());
-#else  // No Atomic64 on 32-bit platforms.
   meta_->sum -= other.sum();
-#endif
 
   HistogramBase::Count old_redundant_count =
       subtle::NoBarrier_Load(&meta_->redundant_count);
   subtle::NoBarrier_Store(&meta_->redundant_count,
                           old_redundant_count - other.redundant_count());
   bool success = AddSubtractImpl(other.Iterator().get(), SUBTRACT);
   DCHECK(success);
 }
 
 bool HistogramSamples::Serialize(Pickle* pickle) const {
-#ifdef ARCH_CPU_64_BITS
-  if (!pickle->WriteInt64(subtle::NoBarrier_Load(&meta_->sum)))
-    return false;
-#else  // No Atomic64 on 32-bit platforms.
   if (!pickle->WriteInt64(meta_->sum))
     return false;
-#endif
   if (!pickle->WriteInt(subtle::NoBarrier_Load(&meta_->redundant_count)))
     return false;
 
   HistogramBase::Sample min;
   HistogramBase::Sample max;
   HistogramBase::Count count;
   for (scoped_ptr<SampleCountIterator> it = Iterator();
        !it->Done();
        it->Next()) {
     it->Get(&min, &max, &count);
     if (!pickle->WriteInt(min) ||
         !pickle->WriteInt(max) ||
         !pickle->WriteInt(count))
       return false;
   }
   return true;
 }
 
 void HistogramSamples::IncreaseSum(int64 diff) {
-#ifdef ARCH_CPU_64_BITS
-  subtle::NoBarrier_Store(
-      &meta_->sum,
-      subtle::NoBarrier_Load(&meta_->sum) + diff);
-#else  // No Atomic64 on 32-bit platforms.
   meta_->sum += diff;
-#endif
 }
 
 void HistogramSamples::IncreaseRedundantCount(HistogramBase::Count diff) {
   subtle::NoBarrier_Store(&meta_->redundant_count,
       subtle::NoBarrier_Load(&meta_->redundant_count) + diff);
 }
 
 SampleCountIterator::~SampleCountIterator() {}
 
 bool SampleCountIterator::GetBucketIndex(size_t* index) const {
   DCHECK(!Done());
   return false;
 }
 
 }  // namespace base